Recently, the manufacturing process has been automatically performed by automated material handling systems (AMHS) such as overhead hoist transports (OHT) or automatic guided vehicles (AGV) in semiconductor manufacturing factories (see, e.g., Japanese Patent Laid-open publication No. 2008-19017).
In an automated material handling system shown in FIG. 1, for example, a plurality of plasma processing devices PM are installed in bay areas B1 to B4 of a manufacturing factory. A plurality of wafers is accommodated per lot in a multi-stepped form in maintenance shelves S1 to S4 (or collectively referred to as S). Rails PP and P1 to P4 are placed between the respective plasma processing devices PM and the maintenance shelves S to enable a plurality of transfer carriages Ve to move on the rails. Carriers taken from maintenance shelves S are loaded on the transfer carriages and are transferred to loading ports of the plasma processing devices PM that execute desired processes. For example, in order to perform a lithography process and then an etching process on wafers, the carrier is firstly transferred to a lithography device to lithograph all wafers in the carrier and the carrier is then transferred to a plasma etching device to etch all the wafers in the carrier.
The processes such as etching and the like are executed per wafer or per lot in the order of a customized recipe. When performing a plasma processing on a product wafer, a pre-treatment (or dummy treatment) such as cleaning, seasoning, or the like may be firstly performed to adjust the conditions of the processing space for the product wafers of next lot. The pre-treatment is also performed in the order of the recipe.
In the pre-treatment such as cleaning, seasoning, or the like, a dummy wafer in the loading port LP or the dummy storage (or dummy maintenance shelf) is typically used instead of the product wafer. Accordingly, it is not necessary that a carrier having the product wafer be inserted into the loading port LP.
Each process including the pre-treatment, however, is executed after it is checked that the carrier is inserted into the loading port LP. Specifically, after the carrier is inserted into the loading port LP, the recipe is first searched and it is checked whether the recipe has the pre-treatment before starting the pre-treatment. After the pre-treatment has completed, the plasma processing of the product wafer is performed. In such a control method, even though the pre-treatment does not need the product wafer, it is impossible to start the pre-treatment before the carrier is inserted into the loading port LP, thereby lowering the throughput. In fact, since the carrier is not guaranteed to be continuously inserted into the loading port LP, the above control becomes hindrance in increasing the productivity.